Wireless sensor networks (WSNs) operate primarily in the 2.4 GHz globally compatible ISM band. However, the wireless propagation channel is notoriously variable and unpredictable, and it has a significant impact on the coverage range and quality of the radio links between the wireless nodes. Therefore, the use of frequency diversity has potential to ameliorate this situation.

This talk will present the method to quantify the possible benefits of using frequency diversity by performing accurate propagation measurements using modified and calibrated off-the-shelf 802.15.4 based sensor motes in the disused underground railway tunnel. Cross correlation coefficients which are calculated from data gathered during the field measurements suggest that applying frequency diversity will improve link performance in a WSN deployed in a tunnel. This finding was confirmed by running a computational simulation of the tunnel radio propagation using a 2D Finite-Difference Time-Domain (FDTD) method.